Effects of the host molecular dynamics on the photoemission temperature dependence of host/guest photoluminescent blends Durval Bertolo Menezes a , Sil  esia de F  atima Curcino da Silva a , Leni Akcelrud b , Teresa Dib Zambon Atvars c , Debora Terezia Balogh d , Yvonne Primerano Mascarenhas d , Alexandre Marletta a , Jos  e Roberto Tozoni a, * a Institute of Physics, Federal University of Uberlandia, P. O. Box 593, Uberlandia, 38400-902, Minas Gerais, Brazil b Paulo Scarpa Polymer Laboratory, Federal University of Parana, P. O. Box 19081, Curitiba, 81531-990, Parana, Brazil c Chemistry Institute, State University of Campinas, P. O. Box 6154, Campinas,13084-971, S~ ao Paulo, Brazil d Institute of Physics of S~ ao Carlos, University of S~ ao Paulo, P. O. Box 369, S~ ao Carlos, 13560-970, S~ ao Paulo, Brazil article info Article history: Received 19 November 2015 Received in revised form 25 February 2016 Accepted 3 March 2016 Available online 4 March 2016 Keywords: Host/guest photoluminescent blends Poly(n-alkyl metacrylate)s Photoemission temperature dependence Molecular relaxations temperatures abstract In the present paper, the photoemission temperature dependence of host/guest blends has been investigated. The polymers blend is composed by poly(n-alkyl metacrylate) (PnMA) as a host and poly [(9,9-dihexyl-9H-fluorene-2,7-diyl)-1,2-ethenediyl-1,4-phenylene-1,2-ethenediyl] (LaPPS16) as a guest. The PnMAs/LaPSS16 blends presented high homogeneity and photoemission temperature stability (T~30 e410 K). Moreover, the PnMA/LaPPS16 blends photoemission in function of sample temperature allowed access to the PnMA molecular relaxations temperatures. This was possible due to the strong interaction between the PnMA n-alkyl side groups and the LaPPS16 aliphatic groups. In addition, the blends films were characterized by Wide-angle X-ray Diffraction, optical absorbance, steady-state photoluminescence spectroscopy, Emission Ellipsometry, and Dynamic Mechanical Analysis. © 2016 Elsevier Ltd. All rights reserved. 1. Introduction Polymer matrices are used often as a dispersive medium for electroluminescent components such as small organic molecules [1,2], quantum dots [3], nano-particles [4], and conjugated poly- mers [5]. Poly(methyl methacrylate) (PMMA), polycarbonate, polystyrene, and polyvinyl carbazole are examples of inert poly- meric matrices used in organic light emitting diodes. One challenge in these systems is to obtain a threshold concentration in which the best device performance can be achieved. When both components of the host/guest system are polymers, the morphology of the resulting blend becomes an important issue. In general, polymer blends are very complex systems due to the usual lower miscibility between the components leading to a phase separation [6]. The luminescent properties of the conjugated polymer in blends or in bilayer systems are not necessarily the same of the pure polymer. For example, the photo and the electroluminescence of some pol- yfluorenes in its pure form, as a guest in the PMMA host [7], or deposited on polyvinyl carbazole surfaces [8], are different due to a partial chain de-aggregation [9]. De-aggregation of the conjugated polymer influences strongly both the emission color and electroluminescence performance. A remarkable example is the electroluminescence enhancement of the poly[(9,9-dihexyl-9H-fluorene-2,7-diyl)-1,2-ethenediyl-1,4- phenylene-1,2-ethenediyl] (LaPPS16) [10] which was increased 18 times in the best blending conditions with polyvinyl carbazole (PVK) (80/20 (w/w) of PVK/LaPPS16), one of the highest values reported so far [11]. Moreover, the great influence of de- aggregation on photo-physical properties of LaPPS16 have been demonstrated in blends with inert matrices of poly(n-alkyl meth- acrylate)s [12]. That effect has been explored due to the significant enhancement on the diode performance, on the thermal and the photochemical stabilities [13,14] and also to the tunability of the emission color in function of the guest concentration [8,13]. In general, improvement in performance is associated to the de- aggregation of the conjugated polymer as a guest [15,16]. Howev- er, the extension of such de-aggregation is very difficult to quantify since, in several cases, the aggregated photoemission has a very low quantum yield [15,16]. The identification of the emitting polymer aggregates at low concentration in host/guest systems is an issue * Corresponding author. E-mail address: rtozoni@infis.ufu.br (J.R. Tozoni). Contents lists available at ScienceDirect Polymer journal homepage: www.elsevier.com/locate/polymer http://dx.doi.org/10.1016/j.polymer.2016.03.009 0032-3861/© 2016 Elsevier Ltd. All rights reserved. Polymer 90 (2016) 132e137